We want to sheet rock out garage but during heavy rain storms it flood

It would be best to get the flood situation taken care of first. French drain, regrading, etc.

First I would deal with the flooding issue before even thinking about drywall. You need drains, sump pumps and even regrading of your property first. Then look into installing insulation and drywall.

You could stop the sheet rock above the level you get in water. Use bricks or cement blocks to finish the lower portion. This should keep the sheet rock dry. We get some water in our garage when it rains real hard. Our property has three steep hilled terraces and the garage is at the base of one. We keep things on pallets. We even have a chest freezer and our large extra fridge that didn't fit in the hole in the kitchen. They keep everything dry so they don't rusty or get soggy and ruined.

You need to fix your flooding problem first, as others have already stated. Otherwise, any drywall will mold and mildew no matter how high you cut it above the cement floor. It's organic. Organisms love eating drywall. And making a mold "all you can eat" buffet with wallboard in an area prone to flooding not only makes an unhealthy area, it creates further damage to your stud walls behind the wallboard by introducing mold into your framing as well

Install the drywall but leave about 6" or so of the bottom NOT dry walled. That gap could then be covered with a very wide base board of vinyl or similar.

All good points. When you get things dry enough to install sheet rock, I suggest using exterior paint if you finish it.

Thanks, we didn't think about using cement blocks. We should be able to seal them on the cement too. Don't want any extra little critters.... LOL Have a great day.

I live on an island so I understand about the flooding that can't be stopped by drains, pumps, etc. We haven't tried to drywall our garage but have been talking about using cement board. That's the stuff they use in showers. You may want to look into that.

Thats where we were looking and then only Thats where we were looking and then only going up 4 inches. I assume that it could be sealed to the floor with a silicone caulking. Thanks